JC virus (JCV) is a human polyoma virus and is the etiologic agent of progressive multifocal leukoencephalopathy (PML), a central demyelinating disease. PML is seen in immunocompromised individuals, suggesting a role for immune mechanisms in controlling disease progression. Approximately 70% of the population exhibit serum antibodies to JCV proteins. Most of the studies to date have focused on determination of humoral immune responses to JCV. The goal of this research project is to investigate the cell-mediated immune responses to JCV in normal healthy individuals. The CD4+ and CD8+ T cell response to the JCV large tumor (T) antigen (Ag) will be examined. T cell cultures will be initiated in vitro with autologous antigen-presenting cells (APCs) that have been "fed" purified T Ag. Virus-infected cells will be used for subsequent T cell stimulations. Two viral systems will be utilized: a recombinant vaccinia virus system and an EBV-expression vector system. T cell function will be analyzed by measuring cytokine release after stimulation with JCV T Ag-expressing cell lines. In addition, CD8+ T cell function will also be determined by cytotoxicity assays. Progress has been made in purifying JCV T antigen, developing the EBV-expression system, and generating vaccinia virus recombinants. The EBV-expression vector has been genetically engineered to express JCV T Ag. In addition. EBV-transformed cell lines have been generated and will be used to express the JCV T Ag from the EBV-expression vector. Once these systems are completed, CD4+ and CD8+ T lymphocyte cultures will be generated and examined for responsiveness to JCV T Ag.